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| United States Patent |
5,524,738
|
|
Erlebach
, et al.
|
June 11, 1996
|
Jaw clutch having profiled jaw clutch elements
Abstract
A jaw clutch for the drive of motor vehicles has a first clutch half and a
second clutch half which are axially displaceable relative to one another,
both clutch halves are provided with axially protruding jaw elements which
are distributed uniformly over the contact surface of the halves. In order
to engage the clutch halves without synchronization and at the greatest
possible difference in speed of rotation in an easy and rapid manner, the
jaw elements are provided with transition zones from the front surface and
side surfaces of the jaw element which are curved as seen in
circumferential section wherein the radius of curvature is 6 to 13%, and
the length of curvature in circumferential direction is 3 to 7% the
average jaw radius.
| Inventors:
|
Erlebach; Friedrich (Steyr, AT);
Leitner; Josef (Kollerschlag, AT)
|
| Assignee:
|
Steyr-Daimler-Puch Aktiengesellschaft (Vienna, AT)
|
| Appl. No.:
|
450368 |
| Filed:
|
May 25, 1995 |
Foreign Application Priority Data
| Current U.S. Class: |
192/69.83; 192/108 |
| Intern'l Class: |
F16D 011/10 |
| Field of Search: |
192/69.8,69.83,108,114 T
|
References Cited
U.S. Patent Documents
| 2384584 | Sep., 1945 | Wildhaber | 192/108.
|
| 2388456 | Nov., 1945 | Wildhaber | 192/108.
|
| 2535388 | Dec., 1950 | Burks et al. | 192/108.
|
| 2654456 | Oct., 1953 | Wildhaber | 192/69.
|
| 3043414 | Jul., 1962 | Peras | 192/108.
|
| 3550738 | Dec., 1970 | Halibrand | 192/108.
|
| 4566566 | Jan., 1986 | Vuillet | 192/69.
|
Primary Examiner: Pitts; Andrea L.
Attorney, Agent or Firm: Bachman & LaPointe
Claims
We claim:
1. A jaw clutch for the drive of a motor vehicle comprising:
a first clutch half and a second clutch half axially aligned along an axis,
said first clutch half being connected to a first wheel drive line of said
motor vehicle and said second clutch half being connected to a main drive
line and a second wheel drive line of said motor vehicle;
said first clutch half and said second clutch half each being provided with
a jaw clutch means on a contact surface thereof, said clutch halves each
having an average jaw radius;
means for axially displacing one of said first clutch half and said second
clutch half along said axis for selectively engaging and disengaging said
jaw clutch means;
said jaw clutch means comprises a plurality of profiled jaw clutch elements
uniformly distributed in spaced relationship on said contact surface of
each clutch half, each of said plurality of profiled jaw clutch elements
has a front surface and a pair of side surfaces, said front surface
comprises a substantially flat central surface between a pair of curved
surfaces each having a length and radius of curvature wherein said curved
surfaces form a transition zone between said flat central surface and said
pair of side surfaces wherein said radius of curvature and length of each
of said curved surfaces is between about 5 to 16% and 3 to 10%,
respectively, the average jaw radius.
2. A jaw clutch according to claim 1 wherein the radius of curvature and
length is between about 9 to 11% and 5 to 7%, respectively, the average
jaw radius.
3. A jaw clutch according to claim 1 wherein the side surfaces are undercut
with respect to said front surface so as to form an angle of about
10.degree. with respect to a line normal to said flat central surface.
4. A jaw clutch according to claim 1 wherein said curved surfaces and said
side surfaces join to form a sharp edge.
5. A jaw clutch according to claim 1 wherein the curved surfaces intersect
the flat central surface at a transition angle of about 21.degree..
6. A distributor having a jaw clutch comprising:
a first clutch half and a second clutch half axially aligned along an axis,
said first clutch half being connected to a first wheel drive line of said
motor vehicle and said second clutch half being connected to a main drive
line and a second wheel drive line of said motor vehicle;
said first clutch half and said second clutch half each being provided with
a jaw clutch means on a contact surface thereof, said clutch halves each
having an average jaw radius;
means for axially displacing one of said first clutch half and said second
clutch half along said axis for selectively engaging and disengaging said
jaw clutch means;
said jaw clutch means comprises a plurality of profiled jaw clutch elements
uniformly distributed in spaced relationship on said contact surface of
each clutch half, each of said plurality of profiled jaw clutch elements
has a front surface and a pair of side surfaces, said front surface
comprises a substantially flat central surface between a pair of curved
surfaces each having a length and radius of curvature wherein said curved
surfaces form a transition zone between said flat central surface and said
pair of side surfaces, said curved surfaces and said side surfaces joining
to form a sharp edge wherein said radius of curvature and length of each
of said curved surfaces is between about 5 to 16% and 3 to 10%,
respectively, the average jaw radius.
7. An axle differential gear having a jaw clutch comprising:
a first clutch half and a second clutch half axially aligned along an axis,
said first clutch half being connected to a first wheel drive line of said
motor vehicle and said second clutch half being connected to a main drive
line and a second wheel drive line of said motor vehicle;
said first clutch half and said second clutch half each being provided with
a jaw clutch means on a contact surface thereof, said clutch halves each
having an average jaw radius;
means for axially displacing one of said first clutch half and said second
clutch half along said axis for selectively engaging and disengaging said
jaw clutch means;
said jaw clutch means comprises a plurality of profiled jaw clutch elements
uniformly distributed in spaced relationship on said contact surface of
each clutch half, each of said plurality of profiled jaw clutch elements
has a front surface and a pair of side surfaces, said front surface
comprises a substantially flat central surface between a pair of curved
surfaces each having a length and radius of curvature wherein said curved
surfaces form a transition zone between said flat central surface and said
pair of side surfaces, said curved surfaces and said side surfaces joining
to form a sharp edge wherein said radius of curvature and length of each
of said curved surfaces is between about 5 to 16% and 3 to 10%,
respectively, the average jaw radius.
Description
BACKGROUND OF THE INVENTION
The present invention relates to jaw clutches for the drive of a motor
vehicle in which a first clutch half is connected to a first wheel drive
line and a second clutch half is connected to a main drive line and a
second wheel drive line wherein one of the two clutch halves is
selectively axially displaceable relative to the other and wherein each of
the clutch halves has axially protruding from a contact surface thereof a
plurality of profiled jaw clutch elements which are distributed uniformly
in spaced relationship over the contact surface.
Jaw clutches are used in distributor gears or differential gears as
described in EP-OS 510 457. The distributor gears can be either with a
central differential or without a central differential. In the former
case, the clutches in question serve as a differential lock and in the
second case they serve to connect the front axle drive. As used herein,
differential gears is understood to mean, in particular, axle differential
gears or intermediate differential gears in vehicles having tandem axles
in which case the clutches in question serve as a transverse lock.
In the application described above, under good road conditions, if neither
locks nor front axle drives are connected, only slight differences in
speed of rotation are present between the clutch halves. Upon worsening
road conditions, the difference in speed of rotation between the clutch
halves increases, which leads to connection or locking. Whether actuated
manually or automatically, as long as the difference in speed of rotation
does not exceed certain limit values, the jaw clutch can be switched
without synchronization. In the case of the gears described in EP-OS 510
457, the engagement of the clutch is effected by an automatic control and
it is possible to leave the disengagement of the clutch to a spring which
operates when the torque drops below a predetermined value.
It is desirable that the range of speeds of rotation at which the jaw
clutch can be engaged be sufficiently large so as to allow for the
engagement to take place as fast and free of friction as possible. The
foregoing saves time during which the vehicle would otherwise lose
momentum or come entirely to a stop.
U.S. Pat. No. 3,550,738 discloses jaw clutches having jaw clutch elements
the front surfaces of which are curved or rounded, as seen in
circumferential section, specifically for the purpose described above. The
curved surface extends over the entire front surface of the jaw clutch
elements and are intended, upon engagement with difference in speed of
rotation of the two clutch halves, to bump past each other with friction
and thus reduce the difference in speed of rotation. This friction means
wear, noise and loss of time. Furthermore, when using a jaw clutch in the
drive line of a vehicle, in which, after all, neither of the clutch parts
rotates freely (the two are coupled by the road more or less rigidly to
each other), the torques are so great that synchronization by such
friction is not possible.
Federal Republic of Germany OS 41 38 917 discloses a jaw clutch having a
profile consisting of circular arcs. In the case of this clutch, the jaws
are held continuously in engagement by a spring which urges the clutch in
closing direction, and they can be disengaged under full load. With the
arcuate profile, no edge pressure occurs during the disengagement of the
clutch halves.
Undercut jaw elements are known from Federal Republic of Germany OS 37 30
889 which discloses clutches which are switched positively in both
directions.
It is the principle object of the present invention to provide a jaw clutch
which can be engaged quickly, reliably, and with low wear, over a
sufficiently large range of differences in speeds of rotation.
SUMMARY OF THE INVENTION
The foregoing object is achieved by way of the present invention wherein
each clutch half is provided with clutch engagement means which comprise a
plurality of profiled jaw clutch elements uniformly distributed in spaced
relationship on the contact surface of each clutch half, each of the
plurality of profiled jaw clutch elements has a front surface and a pair
of side surfaces. The front surface comprises a substantially flat central
surface between a pair of curved surfaces each having a length and radius
of curvature. The curved surfaces form a transition zone between the flat
central surface and the pair of side surfaces, the curved surface and each
of the side surfaces joining to form a sharp edge. The radius of curvature
and length of each of the curved surfaces is between about 5 to 16% and 3
to 10%, respectively, of the average jaw radius, where the jaw radius is
the average distance of the jaws from the axis of rotation. By designing
the profiled jaw clutch elements as aforesaid, the engagement of the
clutch in the desired range of differences in speeds of rotation is
possible while, at the same time, insuring long life. In accordance with
the invention, by providing sharp edges, the jaws are, under the action of
the engagement force, within one another for the shortest time, even
during different speeds of rotations. In other words, the curvature and
the length of the front surface of the profiled jaw elements are so
selected that the jaws of the clutch half which is accelerated in the
direction of engagement (in axial direction) slip as free of friction as
possible past the jaws of the other clutch half. In accordance with the
invention, the front surface and the side surfaces form an edge having a
desired obtuse angle which prohibits the wearing off of the edges of the
jaws.
It has been found by experiment that particularly good results are obtained
if the radius of curvature and the length of the curved surface is
preferably between 9 and 11% and between 5 and 7%, respectively, of the
average jaw radius.
In accordance with a further feature of the invention, the side or flank
surfaces can be undercut by about 10.degree., as seen in circumferential
section, with respect to a line normal to the flat central surface of the
front surface. In this way, on one hand, a favorable contact is obtained
and, on the other hand, assurance is had that the clutch can be reliably
and fully engaged and, once the jaws have been engaged, they will no
longer jump apart.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described below in further detail with reference to
the drawings, in which:
FIG. 1 shows an embodiment of the clutch in accordance with the invention,
seen in longitudinal section, in disengaged condition;
FIG. 2 is an end view along the line 2--2 of FIG. 1;
FIG. 3 is an end view along the line 3--3 of FIG. 1;
FIG. 4 is a circumferential cross section along the line 4--4 in FIG. 2,
shown enlarged;
FIGS. 5, 6 and 7 show three different applications of the clutch of the
invention in the drive line of a motor vehicle.
DETAILED DESCRIPTION
With reference to FIGS. 1, 2 and 3, a first clutch half 1 and a second
clutch half 2 are axially aligned along axis A. The two halves are
connected and fixed for rotation by means of splines 3 and 4 to shafts or
other drive parts (not shown). As illustrated, the second clutch half 2 is
axially displaceable. For this purpose, clutch half 2 is provided with a
circumferential groove 5 for engagement by a gearshift fork (not shown).
The second clutch half 2 has on the contact surface thereof a plurality of
profiled jaws 6 uniformly distributed in spaced relationship and the first
clutch half 1 has the same number of corresponding jaws 7. The spaces
between the jaws 6 and 7 are designated by reference numbers 8 and 9.
The profiles of the jaw clutch elements 6 and 7, as seen in circumferential
section in FIGS. 2 and 3, are formed as follows: With reference to FIG. 4,
each profiled jaw clutch element has a front surface 10 and a pair of side
surfaces 11 and 12. The front surface 10 comprises a flat central surface
between a pair of curved surfaces 16. The curved surfaces 16 form a
transition zone between the flat central surface of front surface 10 and
the side surfaces 11 and 12. Curved surfaces 16 join to the side surfaces
11 and 12 to form a sharp edge 17. Side surfaces 11 and 12 lie
substantially perpendicular to the flat central surface of front surface
10. Preferably, the side surfaces 11 and 12 are undercut with respect to
front surface 10 and form an angle 18 with respect to a line normal to the
front surface of about 10.degree.. The transition 13 between the side
surfaces 11 and 12 and the spaces 8 between profiled jaws 6 and 7 is
rounded so as to reduce notch stresses.
In order to achieve the objects of the invention the profiled jaw elements
must be of a specific geometrical construction. The curved surface 16
extends over a circumferential distance 15 from the edge 17 (which is set
backward in axial direction from the front surface 10 by a relief 14) and
intersects the flat central surface of front surface 10 at a transition
angle 21 of about 5.degree.. The radius of curvature of curved surface 16
is 5 to 16% of the average jaw radius, and preferably 9 to 11%. The
circumferential length 15 of the curved surface 16 is 3 to 10%, preferably
5 to 6%, the average jaw radius. By average jaw radius is meant the radius
25 as shown in FIGS. 1 and 2 from the axis A to the center line of the jaw
elements 6 and 7, that is, the average distance of the jaws from the axis
of rotation. If curved surface 16 has a radius of curvature greater than
described above, there is the danger that the angle formed by the side
surfaces 11 and 12 with the front surface 10 at the edges 17 will be too
small which will result in the edges breaking off.
The radius of curvature 19 of the curved surface 16 is critical. It can be
considered the radius of the osculating circle of a parabola which
describes a point of the clutch half, which clutch half is accelerated
under the action of the engagement force, in case of a given difference in
circumferential speed as compared with the other clutch half. To this
extent, a parabola would be preferable to the circle, but for reasons of
manufacture a circle is preferred. This difference in circumferential
speed corresponds to the difference in the speed of rotation at which the
clutch may still be engaged or disengaged, i.e. in practice about 300 rpm.
The axial relief 14 can be selected arbitrarily, but it should not be
selected too large since it is obtained at the expense of the supporting
surface of the side surfaces 11 and 12. The position of the center 20 of
the circle is determined with the circumferential length 15 of curved
surface 16 at which the arc intersects the front surface 10 at an angle 21
of about 5.degree.. The circumferential length 15 is independent of the
length of the jaw in circumferential direction. For reasons of strength,
the latter will always be substantially greater than the former, so that
the flat central surface of the front surface remains between the curved
surfaces 16.
In the case of higher differences in speed of rotation and small engagement
forces there is a certain danger that the jaws will not pass entirely into
the spaces in the axial direction. In such case, the side surfaces overlap
each other only slightly, and this could lead to the destruction of the
jaws. This can be counteracted by side surfaces which are undercut by an
angle 18 of about 10.degree. and a sharp edge 17, if enlargement of the
circumferential clearance between the jaws of the two clutch parts is not
sufficient.
In FIG. 5, the drive train of a truck consists of a motor with main clutch
40, a transmission 41, and a distributor gear 42 with the input shaft 43.
This forms the main drive line. The distributor gear has a longitudinal
differential 44 from which a first wheel drive line 45 leads to the front
axle and a second wheel drive line 46 leads to the rear axle. For the
locking of the longitudinal differential, a jaw clutch 1 and 2 in
accordance with the invention is arranged between the differential and the
first (in this figure) or the second wheel drive line.
FIG. 6 differs from FIG. 5 only by the fact that the distributor gear does
not have a longitudinal differential, but the first wheel drive line 45
can be connected by means of the jaw clutch 1 and 2 of the invention.
In FIG. 7, a distributor gear 42 may or may not be used. The drive shaft 50
to an axle, in this case the rear axle, forms here the main drive line
which leads to an axle differential 51. 52 and 53 are first and second
wheel drive lines. By connecting one of the two drive lines 52 and 53 with
the differential 51 by means of the clutch 1 and 2 of the invention, the
axle differential can be locked.
It is to be understood that the invention is not limited to the
illustrations described and shown herein, which are deemed to be merely
illustrative of the best modes of carrying out the invention, and which
are susceptible of modification of form, size, arrangement of parts and
details of operation. The invention rather is intended to encompass all
such modifications which are within its spirit and scope as defined by the
claims.
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